1. Field of the Invention
Embodiments of the present invention relate generally to a method and apparatus for evaluating pummeled glass. In one aspect, embodiments of the present invention relate to a method of detecting the nature of light reflected from a sample of pummeled glass and correlating the detected light with light detected from samples of pummeled glass having known pummel adhesion values.
2. Description of Related Art
Common automobile glazing is generally a plural layer laminate having at least one outer transparent glass layer and at least one inner transparent glass layer which are both adhered to an intermediate transparent vinyl or thermoplastic layer. This laminate is often referred to as "safety glass" since the intermediate layer operates to minimize the scattering of glass when the automobile glazing is broken upon impact, i.e. particles of broken glass will generally remain adhered to the intermediate thermoplastic layer rather than being scattered in different directions.
Conventional methods do exist to determine the extent of the bonding strength of a plural layer laminate, such as a paper web to plastic film laminate. See for example U.S. Pat. No. 4,715,718. The standard industry method of evaluating bonding strength within a windshield laminate, however, includes pummeling a test sample of windshield laminate, i.e. impacting a sample cooled to approximately 0.degree. F. with known force so as to break the sample into granular particles, and then visually comparing the test sample itself with samples of pummeled glass having known pummel adhesion values. The operator attempts to visually and, therefore, subjectively match the test sample with a standard pummeled glass sample, and then upon finding a match, assigns the test sample with the pummel value of the matching standard.
One standard set of pummel adhesion values accepted in the industry includes a pummel rating system developed by Monsanto Company (Pummel Adhesion Standards) which rates pummeled glass samples on a scale from 0 to 10 depending upon the nature and extent of adhesion of glass particles to the intermediate thermoplastic layer. Generally, the higher the rating number, the greater the adhesion of the glass particles to the thermoplastic layer.
The standard industry method of evaluating the bonding strength of a windshield laminate, however, includes variability and error often associated with the subjective judgment of the particular individual operator performing the evaluation. The standard industry method, therefore, (1) fails to characterize the quality of pummeled glass samples efficiently and with sufficient repeatability, and (2) fails to minimize the variability and error often associated with a subjective evaluation and comparison of pummel test samples with standard pummel samples. A need therefore exists to develop a method for evaluating pummeled glass which overcomes the deficiencies of the standard industry method.